Basis of Allotment of PAN

Hi members!!!

can i know that on which basis the PAN is allotted.

I know that the Fourth letter of the PAN is Status of the assessee.i.e. Indivdual, Company, firm etc.

and the Fifth letter of the PAn is last name of the person in case of individual and first name of the Person in case of the Firm etc.

but I want to know about the other letters and numbers.